This content is excerpted from Sensor Technology Alert and Newsletter, a sensor intelligence service published by the Technical Insights unit of Frost & Sullivan.
Manifesting the unique properties of carbon nanotubes (CNTs), increasing attention has been paid to the use of single-walled CNTs as a promising electrode material. Therefore, CNT paste electrodes prepared by thoroughly mixing single-walled CNTs and minerals have been seen in a number of instances. Modified with a proper mediator, the resulting electrodes have shown good electrocatalytic activity toward oxidation of reduced nicotinamide adenine dinucleotide (NADH). As a result, a large variety of biosensors and biofuel cells based on NADH cycling can be realized as more than 300 dehydrogenases require this cofactor in their enzymatic reactions. However, one of the main problems related to the direct oxidation of NADH at the electrode surfaces is the high overvoltage required for its oxidation.
Researchers from Dipartimento di Scienze Chimiche, Università di Padova, Padova, Italy, and the Department of Analytical Chemistry, Lund University, Lund, Sweden, have described a new amperometric biosensor for glucose monitoring. The developed biosensor is based on the activity of glucose dehydrogenase and diaphorase co-immobilized with NAD+ into a carbon nanotube paste (CNTP) electrode modified with an osmium functionalized polymer.
The two-member research team has worked on the modification of a CNTP electrode with an osmium redox polymer. The efficient electron shuttling properties of the osmium redox polymers combined with their polymeric structure makes it a very interesting material for electrode modification as it allows easy enzyme co-immobilization. The osmium redox polymer was used to shuttle electrons and also as a support to immobilize diaphorase, glucose dehydrogenase, and the cofactor NAD+ into the CNTP. This helped in developing the glucose biosensor by using poly(ethylene glycol) diglycidyl ether (PEDGE) as a cross-linking agent. The ability to entrap all the enzymes in the redox hydrogel on the electrode surface (which leads to the realization of a reagentless biosensor with a high sensitivity) is due to the use of osmium polymer as redox mediator with PEDGE as a cross-linking agent. Finally, all biosensor elements were integrated on the electrode surface.
The team successfully used the mediated biosensor to determine the glucose content in sweet wine samples. The results obtained were in good agreement with those determined with the standard spectrophotometric method.
According to Riccarda Antiochia, Dipartimento di Scienze Chimiche, Università di Padova, "The preparation of the biosensor is very simple, cheap, and not time consuming. Additionally, it has shown a good linear range, a low detection limit (10 micrometermol/liter), a good reproducibility, and a high stability. It was also inherently not sensitive to the concentration of molecular oxygen. Therefore, we could conclude that all these characteristics make this system a promising example of biosensors, which may represent an interesting alternative to the other most commonly used glucose biosensors based on glucose oxidase for a variety of biotechnological and biofuel cells applications."